We consider the fidelity of the vector meson dominance (VMD) assumption as an instrument for relating the electromagnetic vector-meson production reaction
e
+
p
→
e
′
+
V
+
p
to the purely hadronic ...process
V
+
p
→
V
+
p
. Analyses of the photon vacuum polarisation and the photon-quark vertex reveal that such a VMD
Ansatz
might be reasonable for light vector-mesons. However, when the vector-mesons are described by momentum-dependent bound-state amplitudes, VMD fails for heavy vector-mesons: it cannot be used reliably to estimate either a photon-to-vector-meson transition strength or the momentum dependence of those integrands that would arise in calculations of the different reaction amplitudes. Consequently, for processes involving heavy mesons, the veracity of both cross-section estimates and conclusions based on the VMD assumption should be reviewed, e.g., those relating to hidden-charm pentaquark production and the origin of the proton mass.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The mechanism of superconductivity in cuprates remains one of the big challenges of condensed matter physics. High-Tc
cuprates crystallize into a layered perovskite structure featuring copper oxygen ...octahedral coordination. Due to the Jahn Teller effect in combination with the strong static Coulomb interaction, the octahedra in high-Tc
cuprates are elongated along the c axis, leading to a 3dx²-y² orbital at the top of the band structure wherein the doped holes reside. This scenario gives rise to 2D characteristics in high-Tc
cuprates that favor d-wave pairing symmetry. Here, we report superconductivity in a cuprate Ba₂CuO4-y, wherein the local octahedron is in a very exceptional compressed version. The Ba₂CuO4-y compound was synthesized at high pressure at high temperatures and shows bulk superconductivity with critical temperature (Tc
) above 70 K at ambient conditions. This superconducting transition temperature is more than 30 K higher than the Tc
for the isostructural counterparts based on classical La₂CuO₄. X-ray absorption measurements indicate the heavily doped nature of the Ba₂CuO4-y superconductor. In compressed octahedron, the 3d3z²-r² orbital will be lifted above the 3dx²-y² orbital, leading to significant 3D nature in addition to the conventional 3dx²-y² orbital. This work sheds important light on advancing our comprehensive understanding of the superconducting mechanism of high Tc
in cuprate materials.
Abstract Previous data demonstrate that traumatic brain injury (TBI) activates autophagy, and increases microtubule-associated protein 1 light chain 3 (LC3) immunostaining mainly in neurons. However, ...the role of autophagy in traumatic brain damage remains elusive. The aim of the present study was to investigate the autophagic mechanisms participating in traumatic brain injury. The autophagy inhibitors 3-methyladenine (3-MA) and bafliomycin A1 (BFA) were administered with a single i.c.v. injection before TBI. We first examined the protein levels of Beclin-1 and LC3 II, which have been found to promote autophagy previously. Immunoblotting analysis showed that 3-MA pretreatment reduced post-TBI Beclin-1 and LC3-II levels, and maintained p62/SQSTM1 (p62) levels. In addition, double immunolabeling showed that the increased punctate LC3-II dots colocalizing with Propidium Iodide (PI)-stained nuclei at 24 h after injury, were partially inhibited by 3-MA pretreatment. Furthermore, inhibition of autophagy could reduce TBI-induced cell injury assessed with i.p. injection of PI and lesion volume, and attenuate behavioral outcome evaluated by motor test and Morris water maze. The neuroprotective effects were associated with an inhibition on TBI-induced up-regulation of LC3, Beclin-1, cathepsin B, caspase-3 and the Beclin-1/Bcl-2 ratio. Taken together, these data imply that the autophagy pathway is involved in the pathophysiologic responses after TBI, and inhibition of this pathway may help attenuate traumatic damage and functional outcome deficits.
The megacity of Beijing has experienced frequent severe fine particle pollution during the last decade. Although the sources and formation mechanisms of aerosol particles have been extensively ...investigated on the basis of ground measurements, real-time characterization of aerosol particle composition and sources above the urban canopy in Beijing is rare. In this study, we conducted real-time measurements of non-refractory submicron aerosol (NR-PM1) composition at 260 m at the Beijing 325 m meteorological tower (BMT) from 10 October to 12 November 2014, by using an aerosol chemical speciation monitor (ACSM) along with synchronous measurements of size-resolved NR-PM1 composition near ground level using a high-resolution time-of-flight aerosol mass spectrometer (HR–ToF–AMS). The NR-PM1 composition above the urban canopy was dominated by organics (46 %), followed by nitrate (27 %) and sulfate (13 %). The high contribution of nitrate and high NO3− / SO42− mass ratios illustrates an important role of nitrate in particulate matter (PM) pollution during the study period. The organic aerosol (OA) was mainly composed of secondary OA (SOA), accounting for 61 % on an average. Different from that measured at the ground site, primary OA (POA) correlated moderately with SOA, likely suggesting a high contribution from regional transport above the urban canopy. The Asia–Pacific Economic Cooperation (APEC) summit with strict emission controls provides a unique opportunity to study the impacts of emission controls on aerosol chemistry. All aerosol species were shown to have significant decreases of 40–80 % during APEC from those measured before APEC, suggesting that emission controls over regional scales substantially reduced PM levels. However, the bulk aerosol composition was relatively similar before and during APEC as a result of synergetic controls of aerosol precursors. In addition to emission controls, the routine circulations of mountain–valley breezes were also found to play an important role in alleviating PM levels and achieving the "APEC blue" effect. The evolution of vertical differences between 260 m and the ground level was also investigated. Our results show complex vertical differences during the formation and evolution of severe haze episodes that are closely related to aerosol sources and boundary-layer dynamics.
Summary
We pooled bone mineral density (BMD) data published in 91 articles including 139,912 Chinese adults and then established a national-wide BMD reference database at the lumbar spine and femur ...neck for Chinese adults. The prevalence of osteoporosis in the middle-aged and elderly Chinese population was also estimated.
Introduction
Well-accepted reference value of BMD is lacking in Chinese. We established the reference database and assessed osteoporosis prevalence based on published literature conducted in the Mainland China, Taiwan, and Hong Kong Chinese.
Methods
We searched for all published articles indexed in MEDLINE, PubMed, CNKI, and SinoMed up to January 2013. We included cross-sectional studies that examined BMD using a dual-energy X-ray absorptiometry at the femur neck (FN) and/or lumbar spine (LS) in healthy adults. Overall age-specific mean (SD) BMD were pooled after standardization.
Results
Ninety-one studies including 51,906 males and 88,006 females (≥20 years) in 38 cities in China were included in this pooling study. Gender- and age-specific reference curves of standardized BMD (sBMD) at the LS and FN were constructed. The sBMD cutoffs for osteoporosis classification were 0.746 and 0.549 in women, and 0.680 and 0.568 g/cm
2
in men; age-standardized prevalence of osteoporosis was 23.9 % and 12.5 % in women and 3.2 % and 5.3 % in men aged ≥50 years at the LS and FN, respectively. Meta-regression analysis showed that greater age and altitude, lower latitude, smaller city size, earlier detection time, and random sample were correlated to lower sBMD in at least one gender-specific bone sites; the Hologic DXA produced a higher value of FN sBMD than the other two devices (Lunar and Norland).
Conclusion
We have established a national-wide BMD reference database at the LS and FN for Chinese adults and estimated the prevalence of osteoporosis in the middle-aged and elderly Chinese population.
The susceptible-infected-susceptible (SIS) model is a canonical model for emerging disease outbreaks. Such outbreaks are naturally modeled as taking place on networks. A theoretical challenge in ...network epidemiology is the dynamic correlations coming from that if one node is infected, then its neighbors are likely to be infected. By combining two theoretical approaches-the heterogeneous mean-field theory and the effective degree method-we are able to include these correlations in an analytical solution of the SIS model. We derive accurate expressions for the average prevalence (fraction of infected) and epidemic threshold. We also discuss how to generalize the approach to a larger class of stochastic population models.
Previous studies of geometric and morphologic parameters of intracranial aneurysms have been conducted to determine rupture risk, which remains incompletely defined due to patient-specific risk ...factors, such as sex, hypertension, and age. To this end, we compared characteristics of ruptured and unruptured aneurysms in the same patients with symmetric bilateral intracranial aneurysms.
Between January 2008 and March 2014, 2361 patients with 2674 aneurysms were diagnosed by CT angiography or surgical findings at 4 medical centers. Geometric and morphologic parameters examined for symmetric bilateral intracranial aneurysms comprised aneurysm wall regularity, size, neck width, aspect ratio, size ratio, neck-to-parent artery ratio, and area ratio. Univariate and multivariate statistical analyses were performed to determine independent risk factors for rupture.
Sixty-three patients (48 women, 15 men; mean age, 62.5 ± 9.8 years) with symmetric bilateral aneurysms were eligible for the study and were included. The most frequent aneurysm location was the posterior communicating artery. Univariate analysis disclosed that aneurysm size, aspect ratio, size ratio, area ratio, and irregular wall differed between patients with ruptured and unruptured aneurysms. Multivariate analysis indicated that aspect ratio of ≥1.6 (adjusted OR, 9.521; 95% CI, 2.182-41.535), area ratio of ≥1.5 (adjusted OR, 4.089; 95% CI, 1.247-13.406), and irregular shape (adjusted OR, 10.443; 95% CI 3.394-32.135) were significant predictive factors for aneurysm rupture after adjustment for aneurysm size.
An aspect ratio of ≥1.6, area ratio of ≥1.5, and irregular wall are associated with aneurysm rupture independent of aneurysm size and patient characteristics. These characteristics alone can help in distinguishing ruptured bilateral intracranial aneurysms from unruptured ones.
The development of high-performance ultraelastic metals with superb strength, a large elastic strain limit and temperature-insensitive elastic modulus (Elinvar effect) are important for various ...industrial applications, from actuators and medical devices to high-precision instruments
. The elastic strain limit of bulk crystalline metals is usually less than 1 per cent, owing to dislocation easy gliding. Shape memory alloys
-including gum metals
and strain glass alloys
-may attain an elastic strain limit up to several per cent, although this is the result of pseudo-elasticity and is accompanied by large energy dissipation
. Recently, chemically complex alloys, such as 'high-entropy' alloys
, have attracted tremendous research interest owing to their promising properties
. In this work we report on a chemically complex alloy with a large atomic size misfit usually unaffordable in conventional alloys. The alloy exhibits a high elastic strain limit (approximately 2 per cent) and a very low internal friction (less than 2 × 10
) at room temperature. More interestingly, this alloy exhibits an extraordinary Elinvar effect, maintaining near-constant elastic modulus between room temperature and 627 degrees Celsius (900 kelvin), which is, to our knowledge, unmatched by the existing alloys hitherto reported.
This paper studies the observer-based leader-following consensus of a linear multiagent system on switching networks, in which the input of each agent is subject to saturation. Based on a low-gain ...output feedback method, distributed consensus protocols are developed. Under the assumptions that the networks are connected or jointly connected and that each agent is asymptotically null controllable with bounded controls and detectable, semiglobal observer-based leader-following consensus of the multiagent system can be reached on switching networks. A numerical example is presented to illustrate the theoretical results.
This paper investigates the problem of leader-following consensus of a linear multi-agent system on a switching network. The input of each agent is subject to saturation. Low gain feedback based ...distributed consensus protocols are developed. It is established that, under the assumptions that each agent is asymptotically null controllable with bounded controls and that the network is connected or jointly connected, semi-global leader-following consensus of the multi-agent system can be achieved. Numerical examples are presented to illustrate this result.
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